The disclosure of Japanese Patent Application No. 2005-376773 filed Dec. 28, 2005, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a PCV (positive crankcase ventilation) system for a V-type engine (an engine in which the cylinders are arranged in two separate banks that form a V-shape therebetween).
2. Description of the Related Art
A PCV system separates oilmist from blowby gas using an oil separator, and supplies the oilmist-free blowby gas to an intake system of an engine.
Japanese Patent Application Publication No. 2004-211644 (JP-A-2004-211644) describes providing an oil separator in the upper area of the space between the right and left banks in a V-type engine.
When a surge tank of an intake system is arranged in the upper area of the space between the right and left banks, if an oil separator is provided in the dead space below the surge tank to effectively utilize the space, the oil separator needs to be short in height and flat in order to avoid contact between the oil separator and the surge tank.
FIGS. 7 and 8 show the case where an oil separator 1 that is short in height is arranged in the manner in which the portion, at which the oil separator is connected to the PCV valve, faces the front of a vehicle. In the oil separator 1 that is short in height, the height of a rib 2, on which the blow-by gas containing oilmist impinges so that liquid and gas are separated from each other, is low. Accordingly, an oilmist inlet 3 needs to be formed at an appropriate position so that the size of grains of the oilmist flowing into the oilmist inlet 3 becomes appropriate for gas-liquid separation, or the rib 2 needs to be appropriately arranged so that the length of a blowby gas passage in the oil separator is sufficiently long in order to effectively separate liquid and gas from each other.
If the oil separator 1 that is short in height receives an inertia force due to a sudden stop of the vehicle or if the engine tilts, for example, when the vehicle is running on a downhill slope, oil 4, which has been separated from gas and is on the floor of the oil separator 1 may easily enter a PCV valve 5 provided at the front end of the oil separator 1, flow into an intake manifold, and be burned in the engine. As a result, white smoke may be produced.
In document DE 34 14 710, an engine is disclosed which comprises a valve and an oil separator. Connecting holes connecting the oil separator and a crank case, are formed at the cylinder block. In document EP 0 287 756, an de-aerating means having an oil separator, is placed at the crank case between the cylinders.